Field of the Invention
The present invention relates to an adjusting element for the axial displacement of a camshaft, supported in an axially displaceable fashion, or a camshaft section supported on a shaft and displaceable along the axis of the camshaft. Furthermore, the invention relates to a device for the axial displacement of a camshaft or a camshaft section, comprising an axially displaceable camshaft or an axially displaceable camshaft section, showing one or more projections, and an appropriate adjusting element.
Background of the Invention
Camshafts show a number of cams, which represent eccentric sections on the camshaft. The cams may either be arranged fixed on the camshaft or the camshaft section, which may be applied on the cylindrical shaft in a torque-proof but axially displaceable fashion. Using the cams, adjacently arranged, axially displaceable components may be displaced in regular intervals by rotating the camshaft. A striking application of the camshaft is here given in the opening and closing of valves in an internal combustion engine. In modern internal combustion engines it is possible to change the motor characteristics, for example from a comfort-emphasized to a sporty characteristic, which is implemented, among other things by the change of the valve stroke, determined by the shape of the cams. Additionally, the different engine speeds require variable valve strokes in order to optimize the torque and the fuel consumption. Other internal combustion engines show a cylinder shut-off, in which some of the cylinders can be shut off in order to save fuel. In this case, the valves of the shut-off cylinders no longer need to be opened at all. Here, too, it is not only advantageous to shut off only individual cylinders, but also to allow variable valve strokes for the above-stated reasons. Such internal combustion engines require camshafts, which show cams with different sizes and shapes. A camshaft section of such a camshaft is shown in FIG. 1, with its jacket area being divided into three sections. In a first section a first cam is provided, which opens a valve of an internal combustion engine with a first stroke curve. In a second section a second cam is provided which is smaller in reference to the first cam and which shows a different geometry and thus during the rotation of the camshaft the valve opens with a second stroke curve in reference to the first stroke curve, less widely and for a shorter period of time with a different speed profile. No cam at all is provided in a third section so that a valve cooperating with the first section is not operated at all when the camshaft rotates, which for example is the case when the cylinder is shut off. The camshaft section shown in FIG. 1 respectively illustrates two of these sections, so that for a four-cylinder internal combustion engine two of these camshaft sections must be provided.
In order to allow opening and closing the valve with the different stroke curves, however, the camshaft or the camshaft section must be axially displaced in order to allow the respectively applicable cams to cooperate with the valve. In the solutions of prior art, which are described for example in DE 10 2007 307 232 A1, EP 2 158 596 B1, and DE 10 2013 102 241 A1, the camshafts show different grooves, engaged by an actuator with a different number of tappets. Here the grooves show a guidance section and form, together with the engaging tappets, a gate guide for the axial displacement of the camshaft, which for this purpose must be rotated to a certain extent.
Due to the fact that the tappets of the actuator must be moved to and fro in a coordinated fashion, the actuators are designed in a relatively complicated manner. Additionally, the grooves must be cut into the camshaft, which involves considerable production expenses particularly due to the fact that a separate cam is provided for each tappet, which additionally may show a separate cross-section. Furthermore, the camshaft is weakened in the area in which the grooves are arranged, which increases the probability of a break in this area. This possibility is further increased by stress peaks, which are caused by the cams.
The object of the present invention is therefore to create an arrangement by which a camshaft can be axially displaced in a simply designed fashion.
This object is attained in an adjusting element as described herein.